i need some help bad!!!

ok guys i really need some big help here. i rooted my droid x via z4root last night. from the start i had some bad issues; the first time it didnt work and i hed to turn my fone off and retry. i am not very good with this stuff so please help me out in simple terms. my market will not let me download any paied apps. it says the purchase is invalid and stops at the authorizing purchase loading bar. the rooted apps i currently have are boot animation lite, busybox installer (dont know what it does), superuser (obviously), and z4root. i really want to get a custom rom like sapphire or some other custom rom just to make my fone a little faster, a little more responsive, and look cool. im not a hard core hacker that wants my fone as fast as a super computer, i just want a litle speed and a cool bootup animation and stuff. also i wanted to change my cpu but that app wouldnt download eigther. a list of all the apps i tryed to buy and download are setCPU, root explorer, root tools, boot animation installer, droid boot logo change, rom manager, and droid x recovery bootstrap. i dont know what most of these apps are so please help me out, i just know i need them to change my rom and cpu. what i rele need is someone to teach me what most of this is and help me with my perticular issues. thank you any1 who can help me out! i rele need it.